Various construction materials are used in the construction of decorative and utilitarian fencing. Commonly, wooden fencing is fabricated on site using materials such as cedar, redwood, pine and the like. These fences are constructed by installing posts at spaced-apart intervals, usually set in cement. Horizontal stringers extend between the posts and vertical members in the form of individual pickets or, in some cases pre-constructed panels, are attached to the horizontal stringers. If the vertical members are placed on only one side of the stringers, the fence is a single-sided fence and placement of stringers or panels on both sides of the stringers results in a double-sided fence for improved appearance from either side.
Wooden fences as constructed above are popular because of their appearance and because of general ease of construction. However, in recent years, because of demand and environmental concerns, the cost of wooden fencing materials has risen significantly making these fences expensive. In addition, fences fabricated from wood require periodic maintenance such as painting or application of preservatives or oils.
Another common fencing material is the use of galvanized pipe and wire which systems are popularly termed "cyclone" fencing. Such fencing is primarily used for commercial and industrial applications inasmuch as fencing of this type is not particularly aesthetically appealing.
Block fencing is another popular alternative, particularly in certain parts of the country such as the Southwest. Block fencing construction techniques involve placing a concrete footing including reinforcing at spaced intervals. The block fence is constructed by placing the blocks one at a time in sequential horizontal rows using mortar. Some cement block systems utilize pillars at spaced-apart locations which pillars are formed from blocks mortared in place. Interlocking blocks are used to form the horizontal tiers between the pillars.
While block fences have the advantage of requiring little or no maintenance, block fences are expensive as substantial labor is required to construct the fences. In addition, block fences may be objectionable in hotter climates inasmuch as block will absorb heat throughout the day and radiate heat at night.
Accordingly, fencing contractors have looked to other materials to provide inexpensive yet durable and aesthetically acceptable fencing. Such materials include synthetic materials.
Various fence constructions using synthetic materials can be found in the prior art. For example, U.S. Pat. No. 3,801,072 discloses a fence having the appearance of a picket fence molded from fiberglass. The panels are supported between conventional fence posts to form a fence of synthetic material having the physical appearance of a conventional fence.
U.S. Pat. No. 5,215,290 shows an improved fence made of plastic materials comprising four parts. A central post, removable cap for the post, fence portions and adaptor portions for connecting fence portions with the central post. The adaptor portions have bolt holes oriented in three directions to provide a securing arrangement for the fencing post sections.
U.S. Pat. No. 4,124,198 shows a plastic fence comprising interconnectable post sections including a base post section anchored in the ground and one or more shorter post sections to provide a fence of any desired height. The post sections may be removably interconnected by a screw connection or a bayonet-type connection. In one embodiment, individual struts horizontally connect between spaced post sections while in another embodiment panel means connect therebetween.
U.S. Pat. No. 4,357,000 relates to an integrally molded plastic fence section. Each section is locked to an adjacent section to make up a continuous fence. A plurality of pickets is formed integrally with the stringers. One end of each of the stringers has spaced ears having apertures. The apertures and the ears on one end of a stringer align with the apertures on the other when the fence is assembled.
While the foregoing patents show various fence arrangements utilizing plastic or synthetic materials, none deal with the problem of expansion which occurs in fence pickets made from certain synthetics such as high density polyethylene (HDPE). For example, high density polyethylene has a mind of its own. When the temperature fluctuates 50.degree. F. or so in a twenty-four hour period, this material expands about 1/4" per 8' section. This high rate of expansion has precluded the use of HDPE in most fence applications because expansion eventually causes mechanical fasteners applied between the posts and stringers to tear out. Nails and screws will back out in time weakening the fence and causing components to loosen. Expansion also causes fences to warp and bow creating an unsightly appearance.